The main function of a smear staining machine is for making a blood smear and staining the blood smear if a microscopic examination is needed when abnormal events are found after a routine examination. In the process of making a test sample into a blood smear proper for the microscopic examination, a blood film should be processed for forming a proper appearance with suitable thickness according to characteristics of the sample to configure smearing parameters such as blood drop, smearing speed or smearing angle.
At present, conventional smear technology adjusts smearing parameters mainly based on HCT value of the sample. The HCT value is defined as percentage of red blood cells in certain volume of whole blood, also named as “Hematocrit”. Hematocrit reflects characteristics of the sampling blood in certain perspective, it may look convenient but some disadvantages appear as well at the same time, which are described below. Firstly, characteristics of the sampling blood are not decided by the HCT value only, when HCT value is getting lower, the influence weight of the HCT value from characteristics of the sampling blood is more and more limited correspondingly.
On the other hand, blood plasma and internal suspended matters gradually become main influence factors for characteristics of the sampling blood. All kinds of environment factors, such as environment temperature and humidity, storage period and preservation condition, would influence the configuration of the blood film. For instance, by applying the same blood sample at the same smearing parameters, the blood film would get shorter and thick when the environment temperature is getting lower. On the contrary, the blood film would get longer and thin when the environment temperature is getting higher. In addition, the smear staining machine is designed to process abnormal samples and abnormal samples usually come with high percentage of low HCT value. Therefore, under above conditions, the guiding function of the HCT value for the smear parameters would be reduced accordingly. Improper smear parameters may be acquired if smear parameters are adjusted in accordance with HCT value so as to influence the effect of the blood film process.